Electrolysis utilizing a plurality of electrolytic cells can comprise a bipolar-electrode system or a monopolar-electrode system, depending on the manner of electrical interconnection thereof.
In the bipolar-electrode system, a plurality of electrolytic cells are electrically connected in series, i.e., cathode - anode - cathode - anode - cathode. The series bipolar-electrode electrolytic cell draws relatively low current, although the voltage applied thereto is large. Moreover, electrical interconnection is facilitated and the current is uniformly distributed to the electrolytic cells. However, if the electrolytic compartments of the bipolar-electrode type electrolytic cell are connected by conduits, a stray current arises which by-passes the electrolytic solution. This stray current decreases the efficiency of the electrolytic cell and causes corrosion of valves, piping and other facility components.
On the other hand, in the monopolar-electrode system, the electrolytic cells are connected in parallel such that the current is also distributed in parallel to the electrolytic cells. Thus, although the voltage applied to the monopolar-electrode system is smaller, a larger current is needed. The electric power source is inevitably larger, and the current is not always uniformly distributed to the electrolytic cells.
On weighing the advantages and disadvantages of the bipolar electrode system and the monopolar-electrode system, one system is selected and in order to overcome the above problems, various solutions have been proposed.
In the bipolar-electrode system, leakage current is prevented by strictly separating electrolyte liquids in adjacent electrode compartments. This, however, takes away from the desirable features of the bipolar-electrode system (i.e., simple structure and potential for miniaturization). Even when the electric resistance of electrolyte liquid is particularly large, the above separation is still carried out taking leakage current overly into account.